Drying device



Oct; 6, 1959 M. c. PARKINSON EI'AL 2,907,117

7 DRYING DEVICE Filed Febfls, 1957 2 Sheets-Shet 1 Z INVENTORS MART/Alc. PARK/I60, 5741..

7,9. Mplyg p ATTORNEY O t- 6, 1 59 M. c. PARKINSON ETAL 2,907,117

DRYING DEVICE Filed Feb. 15, 1957 ZSheets-Sheet 2 INVENTORS MARI/4r c.PARK/N50, ETAL.

AT TORA/s Y United States Patent DRYING DEVICE Martin C. Parkinson andDouglas Fraser, Yonkers, and Charles E. Bender, Hastings-on-Hudson, N.Y.

Application February 15, 1957, Serial No. 640,380

2 Claims. (Cl. 34-44) This invention relates to a drying device which isapplicable to the freeze drying process of drying material. However, bythe use of this apparatus, the conventional process of freeze drying issubstantially improved. While this application covers the apparatussolely the improved method is covered in a co-pending application,Serial Number 641,764, filed February 21, 1957.

Conventionally, in the freeze drying process, the material to be driedis placed into a container and then subjected to refrigeration to bringthe material below its freezing point. After the material is frozen(called shell frozen in the conventional process) it is subjected toboth vacuum (which lowers its boiling point) and to radiant heat tocause evaporation of the water'contained in the material. The materialis then reduced to powder and is thereafter removed from the container.

The conventional process, as outlined above, is, as has been shown, atwo stage one. The material must first be shell frozen and then placedunder vacuum and dried.

The conventional process requires the two stage treat- 2,907,117Patented Oct. 6, 1959 centrifugal forces. The details of constructionemployed are set forth broadly in the appended claims.

The invention will be further described by reference to the accompanyingdrawings which are made a part of this specification.

Fig. 1 is a sectional view through the preferred form of the dryingdevice of this invention.

Fig. 2 is a detail view of a form of dryable material container that maybe used where a large bulk of material is to be dried.

Fig. 3 is a sectional view through the vacuum container of thisinvention wherein the dryable material is disposed taken along lines 33of Fig. 1.

Fig. 4 is a somewhat diagrammatic view showing the electrical circuitused in this invention.

The invention will now be described in detail by reference to the formthereof shown in the drawings. However it is pointed out that this formis shown and described for illustrative purposes only and is not to beconstrued as a limitation upon the invention. Various changes andmodifications may be made with regard to the form of this inventionwithout departing from the scope thereof as set forth in the appendedclaims.

The first container of this invention 10, wherein the dryable materialis disposed, is made of transparent material such as glass. At itsbottom portion 11 a seal 12 is provided which is preferably made ofresilient rubber or rubber-type material.

A conduit 13 passes through the base 80 upon which container 10 rests,and also opens into container 14 which is made of metallic conductivematerial. An additional conduit 15 also opens into container 14 and inturn is secured to vacuum pump 16.

An additional conduit 9 opens into container 14 and joins gauge 21,which indicates the pressure within con- 7 tainers 10 and 14, tocontainer 14.

ment for the reason that substantial reduction of the pressure above theliquid material would cause the same to froth and foam. This would causesplashing of the liquid and severe material losses.

We have discovered that such frothing and foaming can be prevented evenif the material is placed under vacuum in liquid form. In order to dothis, however, it is necessary to apply centrifugal force to thematerial at the same time.

In order to apply centrifugal force and vacuum to materialat the sametime, it is clear that the material must be placed within a closedsystem within which it may be subjected to the centrifugal force.Conventional centrifugal force producing devices are operated fromwithout the system and generally extend without the system. Thus, if aconventional device is used, a rotary seal must be provided to preventthe inrush of air into the system. Such rotary seals are generallyunsatisfactory and prevent adequate vacuum or centrifugal forceconditions from being maintained.

Before closing this preliminary exposition of the invention it ispointed out that the word vacuum as used in the specification and claimsrelating to this invention does not mean the total absence of air in thesystem. The word is intended to cover the conditions produced by theremoval of a major quantity of the air in the system so that a very lowpressure is produced therein.

The invention may be briefly described as comprising, in combination, acontainer having vacuum producing means, refrigerating means and radiantheat producing means in operative relationship therewith. Centrifugalforce producing means are located within the container and are actuableupon dryable material placed therewithin. Novel constructional featuresare employed so that the device is operable under low pressures and highA valve 8 is disposed within conduit 9 between container 14 and gauge21. Valve 8 is normally closed but, when open, permits conduit 9 tocommunicate with the atmosphere. Thus valve 8 acts as a venting devicewhen I it is desired to open container 10.

Gauge 21 is in series with wires and 101 which are part of the circuitconsisting of wires 100, 101, switch 102, wire 103, vacuum pump 16, andwire 104. Gauge 21 also constitutes pressure responsive control means.By

. means of these means gauge 21 may be set for any predeterminedpressure and controls the conditions within container 10 by turning pump16 on and off.

A coil 17, which bears an expanding refrigerant, is disposed aboutcontainer 14. Coil 17 in turn is connected to compressor 18 andcondenser 19. The conventional valve 20 regulates the flow ofrefrigerant into coil 17. A thermostat 6 is in series with wires 105 and106 which are part of the circuit consisting of wire 104, compressor 18,wire 106, thermostat 6, wire 105, switch 107, wire 108 and wire 100.Thus thermostat 6, which may be set to any predetermined temperature,controls the same by turning compressor 18 on and off. The sensing meansfor thermostat 6 are located within container 14. For clarity ofillustration of the remaining elements of this invention these sensingmeans are not shown in Figs. 1-3 of the drawings.

A fixed vertical support 22 is centrally located within container 10. Arotatable vertical support 23 is disposed above support 22 and bearsshelves 24 and 25 thereupon. Bottle holding supports 26 are disposed inspaced relationship upon shelves 24 and 25.

A motor 27 is disposed within support 22. Wires 28 and 29 are connectedto motor 27 and pass through seal 12. Wire 29 is in series with rheostat111 and wire 112 at its upper end thereof. Key portion 32 fits into amating groove 33 located within rotatable support 23. A hearing 33 isdisposed between key shaft 32 and rotatable support 23.

A radiant heat device 34, comprising an infra-red incandescent bulb islocated without container and is supported upon support 35. A socket 36is provided upon support 35 so that bulb 34 can be directed into rayimpinging relationship withthe dryable material con tained withincontainer 10. Bulb 34 is also connected to a power source. The circuitinvolved comprises Wire 113, rheostat 114, wire 115a, switch 116, wire117, wire 110, wire 104 and Wire 100.

Fig. 2 of the drawings shows the form of material container that may beused where a large volume of material is to be dried. As shown herein acylindrical container 36 hearing offset portions 37 is secured tosupport 23.

The operation of this invention will now be explained.

Container 10 is removed from seal 12 and a number of bottles of materialto be dried 38 are placed Within Supports 26. Container 10 is thenplaced upon seal 12 and valve 8 is closed. Gauge 21 is set to thepressure desired and switch 102 is closed starting vacuum pump 16. Atthe same time thermostat 6 is set to the desired temperature and switch107 closed starting compressor 18. Rheostat 111 is set to the desiredrotational speed (about 1450 rpm.) and switch 109 closed thus startingmotor 27 and producing centrifugal force. Generally the pressureproduced is about .005 mm. and the temperature about 20 C.

After a period of about 3 minutes the material contained in bottles 38is frozen. At this point it is no longer necessary to apply largecentrifugal forces to the material since there is no danger of foamingand splashing. Rheostat 111 is then turned to reduce the speed ofrotation of motor 27 so that bottles 38 now turn at a speed of about 3rpm. Switch 116 is then turned on so that infra-red heat produced bybulb 34 impinges upon bottles 38. The intensity of the heat produced bybulb 34 is controlled by rheostat 114. The intensity used depends uponthe material dried.

The conditions of pressure, temperature, and external heat are continueduntil the material contained in bottles 38 is reduced to powder form.When this occurs switches 102, 107, 109, and 116 are turned off andvalve 8 is opened venting the container 10 to the atmosphere. Container10 is then removed from seal 12, bottles 38 removed, and the apparatusis ready for the next cycle.

We claim:

1. A drying device comprising a first transparent container, a subjacentsecond metallic container, a conduit joining said first and secondcontainers, a refrigerant hearing coil surrounding said secondcontainer, a vacuum pump connected to said second container, a fixedvertical support member centrally within said first container, anadditional rotatable vertical support member supported by said fixedsupport, a substantially horizontal dryable material container securedto said rotatable support, an electrical motor within said firstcontainer and supported by said rotatable support adapted to rotate thesame and to thereby apply centrifugal force to said dryable materialcontainer, and an electrical radiant heat producing bulb without saidfirst container, in spaced relationship thereto, and in ray impingingrelationship with said dryable material container.

2. A drying device comprising a first transparent container, a subjacentsecond metallic container, a conduit joining said first and secondcontainer, a refrigerant bearing coil positioned within and contiguousto the wall of said second container, a vacuum pump operativelyconnected to said second container, pressure responsive control meansoperatively connected to said second container adapted to actuate saidvacuum pump and thus control the pressure within the system,thermostatic control means within said second container adapted toactuate said refrigerant bearing coil and thus control the temperaturewithin the system, a fixed vertical support member located centrallywithin said first container, an additional rotatable vertical supportmember overlying said fixed support, a substantially horizontal dryablematerial container secured to said rotatable support, an electricalmotor operatively connected to said rotatable support adapted to rotatethe same and thereby apply centrifugal force to said dryable materialcontainer, rheostat means operatively connected to said motor, and anelectrical radiant heat producing bulb Without said first container, inspaced relationship thereto, and in ray impinging relationship with saiddryable material container.

References Cited in the file of this patent OTHER REFERENCES Greaves:Centrifugal Vacuum Freezing, Nature, vol. 153, p. 485 (April 22, 1944).

